Concrete block making machines with vented cores carried by the vibrating molds of the machines are well known and disclosed, for example, in U.S. Pat. Nos. 2,566,787; 3,608,162; and 4,235,580, which illustrate various prior art constructions. The foregoing United States patents are incorporated herein by reference.
The new style ventilation pin system to be described herein substantially reduces the amount of material spillage due to a more precise alignment of the pins with the pin ventilation openings in the top wall of the core assembly and so is saving of material, eliminates prior art manufacturing and assembly problems, and considerably reduces the assembly time required to mount the pin systems in place.
The pin system of the present invention utilizes pin cups, supported by the core plate, which depend into the hollow cores or shells which provide the cavities in concrete blocks, for example. Ventilation providing displaceable pins have heads which are received within the cups to slide up and down in a state of alignment with the cups, and springs are provided between the shanks of the pins and the lower ends of the cups to normally maintain the pins in a position in which the heads of the pins plug the upper ends of the cups when the pallet is bearing on the pin shanks to compress the springs. The pins are designed to plug off the ventilation openings during filling of the mold and during the product compacting and densifying vibration.
The cup walls have slotted external grooves between their upper and lower ends which, when the pin heads descend below the level of the upper ends of the grooves communicate the atmosphere outside the mold with the grooves to admit vacuum breaking air to the interior of the core shells so that they can be readily withdrawn without tending to crumble the block or product formed in the mold during the block stripping operation. As a result of this, suction forces, which otherwise would build within the cavities of the hollow core shells, are relieved by the air flowing in from outside. This vacuum breaking operation occurs when the stripper shoes and pallet receiver move downwardly and the pins are displaced downwardly by the return springs which were compressed by the pallet when it initially was moved upwardly to close the bottom of the mold.